Dry plate rectifier



?atented Apr. 30, 1935 UNITED STATES DRY PLATE RECTIFIER Willem Christiaan van Geel and Hendrik Emmens, Eindhoven, Netherlands, assignors to Radio Corporation of Delaware Application October 7,

America, a corporation of 1931, Serial No. 567,417

In the Netherlands October 8, 1930 4 Claims.

This invention relates to a dry plate rectifier. A s a rule rectiers of this type are constituted by two plate or strip shaped electrodes consisting of vdifferent materials and separated by a thin intermediate layer consisting of a third material. In many cases one electrode is made of a metal and coated with an oxide of the metal constituting the intermediate layer between both electrodes. However, also other intermediate layers are used.

It sometimes appears that recters which have perfectly Worked for a long time, abruptly lose their rectifying properties and consequently allow the passage of a current in both directions. This is probably due to puncturing of the intermediate layer between the outer electrodes.

According to the invention this drawback is successfully counteracted by adding a material yielding oxygen to the material of which one of the electrodes is made.

It is not advisable to make the whole electrode of such a material, since the properties of this electrode and the rectifying effect of the Whole electrode system would be unfavourably affected thereby.

As a material yielding oxygen it is advantageous to use KClOa, BaOz or KMnOr, though various other materials yielding oxygen are also adapted for this purpose.

In front of the electrode provided with a material yielding oxygen may be placed electrodes consisting of diierent materials, in particular a metal electrode. Among the proper metals are first of all mentioned the metals of the rst sub group of`the fourth principal group which includes thorium, zirconium and titanium. The latter two are especially useful since these metals may be provided in a comparatively simple manner with a perfectly coherent, thin, stable oxide layer.

Furthermore the present invention permits of obtaining a` considerable simplification of the electrode system. In fact, it has been found,

that an excellent rectifier may be obtained by' making one outer electrode of magnesium, aluminum or of an amalgam of these materials and by pressing this electrode directly against the other outer electrode consisting of a mixture of one or more sulfur compounds and a material yielding oxygen, for example, of a mixture of cuprous sulfide, cupric sulfide and potassium permanganate.

In such a rectifier an insulating intermediate layer is probably formedimmediately on pressing both electrodes one against the other, thus obtaining a rectier without special means being required for forming an intermediate layer. Thereby the previous oxidation of the magnesium or of the aluminum is rendered superfluous which consequently entails an economy in the cost of production.

The invention will be more clearly understood by reference to the accompanying drawing, representing, by way of example, an electrode system with unsymmetrical conductivity according thereto.

Fig. l is a cross section of the rectifler in which also the electric connections are schematically shown. Y

Fig. 2 is a corresponding front view.

The plate l consists, for example, of zirconium. and is coated on one side with an oxide layer 2, on which bears the plate 3 consisting, for example, of a mixture of copper iodide and barium peroxide. These materials are pressed in powder on a copper gauze 4. In the drawing is shown that this copper gauze which essentially serves for obtaining a thin and yet firm plate shaped electrode, is used at the same time as a connection for the conductor 5.

The current passes only in the direction of the electrode 3 to the electrode I. During the time in which the upper terminal B of the source of alternating current is positive, the current consequently flows from 6 through the conductor 5, the copper gauze 4, the plate 3, the plate I, the conductor 8, the direct current terminals 9 and the conductor IIJ to the other terminal 'l of the source of alternating current. During the next half period no current passes consequently the direct current load receives a pulsatory direct current.

It will be appreciated that by assembling different rectifying cells, for example, in Grtzor Greinacher-connection, also both halves of the alternating current period may be rectied.

Of course, the invention holds also good for electrodes consisting of materials otherr than those referred to above. As a cathode also copper or calcium may be used instead of using one of the metals of the first sub group of the fourth principal group. Among the materials of which the anode may consist, phosphorus lead sulfide, molybdenum sulfide, iron hammer scale, sesquioxide of manganese, silver chloride or mixtures of these materials are mentioned.

What we claim is:-

1. In electric current rectiers of the dry surface contact variety, an asymmetric couple having positive and negative electrodes, one of said electrodes comprising at least one of the metals of the rst sub-group oi.' the fourth periodic group, the other of said electrodes comprising an oxidizing agent mixed with an electrode material comprising at least one of a group of com.-

`the iirst sub-group of the fourth periodic group,

the other of said electrodes comprising a powerful oxidizing agent chosen from the oxidizing agent group including potassium chlorate, barium dioxide, potassium permanganate mixed with In electrode material comprising at least one of a group of components including sulphides and iodides.

4. An asymmetric couple having positive and negative electrodes said positive electrode including at least zirconium, the other electrode of said 1o couple comprising a mixture ot copper iodide and barium peroxide, said last named mixture being ground and pressed on a metallic gauze, and a layer of oxide between said two plates, said layer of oxide being formed by the contact of said two 16 plates.

WILLEM CI-IRISTIAAN VAN GEEL. HENDRIK EMMENS. 

